The Official 4/26/13 MCAT Thread

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In lieu of the other threads popping up, I thought it'd be good for those of us taking the test to identify ourselves 👍

I'm not planning on following a rigid study schedule until January, but I think I'm going to watch a single video off of wikipremed daily to lightly review.

Good luck to everyone... we will crush this exam..

 

[Status Sciaticus]

The funny part is that a huge chunk of the posts will come on test day... We will easily beat out 3/23's thread.

 

[WSHRocks]

I don't think we'll beat 03/23 any time soon, but we can try coming close. #4 spot is a pushover already with a difference between us and them of like 9 posts.

 

[Status Sciaticus]

I don't think we'll beat 03/23 any time soon, but we can try coming close. #4 spot is a pushover already with a difference between us and them of like 9 posts.

dont be a negative nancy....


what happens to angular velocity, angular acceleration, and torque as you move from the edge of a rotating circle inwards?

 

[Albein]

dont be a negative nancy....


what happens to angular velocity, angular acceleration, and torque as you move from the edge of a rotating circle inwards?

off the top of my head i think torque decreases because the lever arm (radius) decreases, acceleration increases? because a=v squared/r
not sure about angular velocity.

i could be dead wrong about this so someone correct me if i am.

edit: is angular velocity=v/r? so i think that would also increase.

 

[milski]

dont be a negative nancy....


what happens to angular velocity, angular acceleration, and torque as you move from the edge of a rotating circle inwards?

Angular velocity/acceleration stay the same, the magnitude o the torque (with respect to the axis) decreases since the arm decreases.

 

[osprey099]

dont be a negative nancy....


what happens to angular velocity, angular acceleration, and torque as you move from the edge of a rotating circle inwards?

torque should decrease because moment arm decreases. torque = force * moment arm

angular velocity should stay the same because angular velocity is only a measure of how fast theta is changing and it is changing the same degree/second no matter the radius

angular acceleration stays the same because angular velocity doesnt change.

 

[Albein]

torque should decrease because moment arm decreases. torque = force * moment arm

angular velocity should stay the same because angular velocity is only a measure of how fast theta is changing and it is changing the same degree/second no matter the radius

angular acceleration stays the same because angular velocity doesnt change.

Thank you. I wasn't entirely sure because going based on the formula didn't feel right in my gut.

Edit: why can't we use angular velocity=v/r to figure it out? If the linear velocity remains constant and radius decreases, wouldn't angular velocity increase?

 

[osprey099]

Thank you. I wasn't entirely sure because going based on the formula didn't feel right in my gut.

Edit: why can't we use angular velocity=v/r to figure it out? If the linear velocity remains constant and radius decreases, wouldn't angular velocity increase?

I believe angular velocity should be the same at all points on a rotating disk. This is because angular velocity is fundamentally a measure of the change in pheta as a function of time. This change in pheta is the same at all points on a rotating disk.

 

[Albein]

I believe angular velocity should be the same at all points on a rotating disk. This is because angular velocity is fundamentally a measure of the change in pheta as a function of time. This change in pheta is the same at all points on a rotating disk.

Fair enough. I just assumed since there was more than one formula, we could use that to determine what would happen. I'll have to go back to BR and take another look at it.

 

[osprey099]

Fair enough. I just assumed since there was more than one formula, we could use that to determine what would happen. I'll have to go back to BR and take another look at it.

Yea I am not entirely sure either because this brings the question of why a ballerina's angular velocity increases when she pulls her arms in (decreases the radius)?

 

[LaughingMan]

Anyone mind sharing what they are putting on their "dump sheet," for those 10 minutes during the tutorial?

When I sit down, I usually just put a few optics charts and equations. Feel like I should be putting alot more.

 

[Innie]

I haven't been studying like crazy, just trying to get in a few good hours a day.
My plan for today is to finish reviewing bio (which is my weakest section, I've got 3 out of 12 chapters left of the princeton review book) and go over all the equations in PS, then do AAMC 11.

So that's like ~6 hrs of work in a day where I literally have nothing else to do because I took the whole week off.
And tomorrow I'm going SHOPPING. Forget studying the day before. Make yourself happy and get a cute outfit for test day. Maybe I'll fail this thing but I'll be the best dressed one there!

 

[Status Sciaticus]

lets keep these questions going... it can only help...

 

[Temperature101]

Can someone tell me how to buy the AAMC CBT tests? I went to the website and I could not find the link to order them...

 

[Status Sciaticus]

I believe angular velocity should be the same at all points on a rotating disk. This is because angular velocity is fundamentally a measure of the change in pheta as a function of time. This change in pheta is the same at all points on a rotating disk.

Fair enough. I just assumed since there was more than one formula, we could use that to determine what would happen. I'll have to go back to BR and take another look at it.

torque should decrease because moment arm decreases. torque = force * moment arm

angular velocity should stay the same because angular velocity is only a measure of how fast theta is changing and it is changing the same degree/second no matter the radius

angular acceleration stays the same because angular velocity doesnt change.

Angular velocity/acceleration stay the same, the magnitude o the torque (with respect to the axis) decreases since the arm decreases.

The correct answer according to TBR physics pg 84.

1. torque decreases because of the decrease in the moment arm (radius)
2. velocity DECREASES because since the rotating circle has a fixed period, a longer radius will travel more distance in the same time than a smaller circle will.
3. acceleration DECREASES because velocity decreases.

 

[WSHRocks]

Yea I am not entirely sure either because this brings the question of why a ballerina's angular velocity increases when she pulls her arms in (decreases the radius)?

The ballerina example has to do with moment of inertia. If the axis of rotation is centered on the body, extending the arms will increase inertia (resistance to movement) by increasing the mass that is at a certain radius from the center. By bringing the arms closer to the body, inertia is decreased. I don't think this is covered though, right? About rotational motion, as I understand it angular velocity for a spinning disk won't vary at any particular radius, but the linear velocity will. Angular acceleration would then be based on if the velocity is changing or not.

I'll add here that the increase of speed of the ballerina with both arms in is based on conservation of angular momentum (L=Iw, where I is moment of inertia and w is angular velocity).

 

[osprey099]

The ballerina example has to do with moment of inertia. If the axis of rotation is centered on the body, extending the arms will increase inertia (resistance to movement) by increasing the mass that is at a certain radius from the center. By bringing the arms closer to the body, inertia is decreased. I don't think this is covered though, right? About rotational motion, as I understand it angular velocity for a spinning disk won't vary at any particular radius, but the linear velocity will. Angular acceleration would then be based on if the velocity is changing or not.

I'll add here that the increase of speed of the ballerina with both arms in is based on conservation of angular momentum (L=Iw, where I is moment of inertia and w is angular velocity).

Ok I understand now. The ballerina example is an entirely different topic (rotational inertia), which I don't think is covered on MCAT. But yea, angular velocity for spinning disk is same at all points but I don't understand why Gandalf said that it should decrease..

 

[osprey099]

The correct answer according to TBR physics pg 84.

1. torque decreases because of the decrease in the moment arm (radius)
2. velocity DECREASES because since the rotating circle has a fixed period, a longer radius will travel more distance in the same time than a smaller circle will.
3. acceleration DECREASES because velocity decreases.

Are you sure they were talking about angular velocity and not linear velocity?

 

[MedGrl@2022]

We are 5th on the forums as far as replies goes. I think we have potential...

30 on AAMC 11!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I don;t know how but I did it I did it... 🙂

I actually restarted the PS section because I need to be mindful of my time but here is the break down

10 PS/ 9 VR/ 11BS...

BS was hard... I don't know how I pulled the 11 off... lots of great guessing I guess

My VR score FINALLY went up...

Gotta be more mindful of my time on the real thing...

Can we go over AAMC 10 and 11 on this thread since not a lot of people seem to be responding on the MCAT Q&A... I am going to start reviewing soon!

 

[milski]

The correct answer according to TBR physics pg 84.

1. torque decreases because of the decrease in the moment arm (radius)
2. velocity DECREASES because since the rotating circle has a fixed period, a longer radius will travel more distance in the same time than a smaller circle will.
3. acceleration DECREASES because velocity decreases.

The ballerina is a different situation - it's the equivalent of replacing the disc with a smaller disk with the same mass, not just considering a different point on the disk.

You can use v/r but keep in mind that the linear velocity also decreases as the radius decreases.

 

[osprey099]

3
Can we go over AAMC 10 and 11 on this thread since not a lot of people seem to be responding on the MCAT Q&A... I am going to start reviewing soon!

Sure, which questions did you want to go over?

 

[Status Sciaticus]

Are you sure they were talking about angular velocity and not linear velocity?

Ill look at the TBR example again, but i think it refers to tangential velocity now that I think about it....

even if it does talk about tangential velocity.... angular velocity should still be affected because the equation is w=v/r where v is tangential velocity and w is angular velocity right?

 

[Albein]

Ill look at the TBR example again, but i think it refers to tangential velocity now that I think about it....

even if it does talk about tangential velocity.... angular velocity should still be affected because the equation is w=v/r where v is tangential velocity and w is angular velocity right?

That was my logic too. Yeah w is angular and v is linear (tangential) velocity

 

[WSHRocks]

Ill look at the TBR example again, but i think it refers to tangential velocity now that I think about it....

even if it does talk about tangential velocity.... angular velocity should still be affected because the equation is w=v/r where v is tangential velocity and w is angular velocity right?

You should rely more on a conceptual explanation than the equation. If you have a record that spins at 33 1/3 rpm (frequency, where 2pi*f=w) and you mark a line that extends from the center to the edge, any point along that line will rotate in a full circle from the starting point in the same time as any other point on that line. Angular velocity relates to the circular displacement rather than the linear displacement here.

 

[osprey099]

Ill look at the TBR example again, but i think it refers to tangential velocity now that I think about it....

even if it does talk about tangential velocity.... angular velocity should still be affected because the equation is w=v/r where v is tangential velocity and w is angular velocity right?

you can't rely on that equation. Like WSH said, angular velocity is fundamentally a measure of the change in theta (angle) as a function of time.

 

[chickensoupdr]

I wonder if it's possible to just start a group chat room thing. I'm going to be going over AAMC 9, 10, 11 today as well.

30 on AAMC 11!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I don;t know how but I did it I did it... 🙂

I actually restarted the PS section because I need to be mindful of my time but here is the break down

10 PS/ 9 VR/ 11BS...

BS was hard... I don't know how I pulled the 11 off... lots of great guessing I guess

My VR score FINALLY went up...

Gotta be more mindful of my time on the real thing...

Can we go over AAMC 10 and 11 on this thread since not a lot of people seem to be responding on the MCAT Q&A... I am going to start reviewing soon!

 

[MedGrl@2022]

I wonder if it's possible to just start a group chat room thing. I'm going to be going over AAMC 9, 10, 11 today as well.

Let me know if you figure this out! I am down!

 

[MedGrl@2022]

Sure, which questions did you want to go over?

PS Item 1 (Passage I) AAMC 11:

The electrochemical cell can be operated at atmospheric rather than high pressure because:

A) Le Chatelier's principle does not apply to reactions in electrochemical cells.
B) electrical work serves to drive the reaction
C) SCY catalyzes the reaction
D) oxidation-reduction processes are unaffected by pressure

I thought B made sense but then I went with D because I thought it was the "better" answer... apparently it wasn't.

Are oxidation-reduction processes affected by pressure?

 

[Back 5]

The more I read the 3/23 thread and those people who did very poorly compared to their aamc average...the more I feel we will be okay. It seems that some of the people in 3/23 either used their most recent aamc averages after a retake, which inflated their scores, or they only took a couple of the aamc tests and did not take #10 and #11.

This is just my opinion, but if you have a body of evidence (aamc #3-11 as well as guidebook) and your scores all fall within a close average, then you should score close to that on the MCAT Friday.

I really hope I can quote this post in a little over a month and we are all pleased with our results 🙂

Only you can know if you were taking the practice tests under MCAT conditions though. There is no "peaking" during the real MCAT. No Google. No notes etc etc etc. All of this will lead to an inflated score and a potential drop in your MCAT score versus your aamc averages.

 

[HotHamH2O]

Let me know if you figure this out! I am down!

this would be great...we could just drop questions at each other this evening

 

[Back 5]

PS Item 1 (Passage I) AAMC 11:

The electrochemical cell can be operated at atmospheric rather than high pressure because:

A) Le Chatelier's principle does not apply to reactions in electrochemical cells.
B) electrical work serves to drive the reaction
C) SCY catalyzes the reaction
D) oxidation-reduction processes are unaffected by pressure

I thought B made sense but then I went with D because I thought it was the "better" answer... apparently it wasn't.

Are oxidation-reduction processes affected by pressure?

Electrolytic cell requires electricity to drive the reaction. This is why they are not spontaneous. The question doesn't specifically call it an electrolytic cell, but the passage did.

 

[osprey099]

PS Item 1 (Passage I) AAMC 11:

The electrochemical cell can be operated at atmospheric rather than high pressure because:

A) Le Chatelier's principle does not apply to reactions in electrochemical cells.
B) electrical work serves to drive the reaction
C) SCY catalyzes the reaction
D) oxidation-reduction processes are unaffected by pressure

I thought B made sense but then I went with D because I thought it was the "better" answer... apparently it wasn't.

Are oxidation-reduction processes affected by pressure?

The answer is B because the passage directly states that the reaction is driven by a electrochemical cell. Pressure is a form of Le-Chatlier and Le-Chatlier affects all types of reactions, including ox-red rxns.

Also, an easy way to eliminate answers is noticing that choices A and D are saying the same thing, so they are both eliminated immediately.

 

[MedGrl@2022]

Electrolytic cell requires electricity to drive the reaction. This is why they are not spontaneous. The question doesn't specifically call it an electrolytic cell, but the passage did.

so basically pressure isn't involved at all? Why isn't D a valid answer?

 

[Back 5]

so basically pressure isn't involved at all? Why isn't D a valid answer?

It might very well be a valid answer, but B is more correct, therefore B is the best answer.

 

[MedGrl@2022]

The answer is B because the passage directly states that the reaction is driven by a electrochemical cell. Pressure is a form of Le-Chatlier and Le-Chatlier affects all types of reactions, including ox-red rxns.

Also, an easy way to eliminate answers is noticing that choices A and D are saying the same thing, so they are both eliminated immediately.

Booo!!! So A and D are correct answers... but B is the best answer?

 

[HotHamH2O]

The more I read the 3/23 thread and those people who did very poorly compared to their aamc average...the more I feel we will be okay. It seems that some of the people in 3/23 either used their most recent aamc averages after a retake, which inflated their scores, or they only took a couple of the aamc tests and did not take #10 and #11.

This is just my opinion, but if you have a body of evidence (aamc #3-11 as well as guidebook) and your scores all fall within a close average, then you should score close to that on the MCAT Friday.

I really hope I can quote this post in a little over a month and we are all pleased with our results 🙂

Only you can know if you were taking the practice tests under MCAT conditions though. There is no "peaking" during the real MCAT. No Google. No notes etc etc etc. All of this will lead to an inflated score and a potential drop in your MCAT score versus your aamc averages.

IDK if intellectual challenges are anything like physical ones, with a nice rest day tomorrow and well controlled anxiety on test day, it is possible that you could peak. This has happened to me many times competing as a cyclist. I would feel terrible training all week before a big race, and then come race day when it really counts, i would put my head down and just feel good the whole race. theres a study on anxiety and cognitive abilities. anxiety gradually increases cognitive ability but then drops off like a cliff at a certain blood pressure and pulse rate. the study was conducted on trauma hospital staff during pediatric emergencies. ill look it up.

 

[osprey099]

Booo!!! So A and D are correct answers... but B is the best answer?

A and D are both wrong. LeChatlier affects all reactions. Pressure is a form of LeChatlier. So its temperature, volume, concentration of reactants and products.

Edit: What I was saying earlier is that since A and D are saying the same thing, both can be eliminated immediately.

 

[Back 5]

Booo!!! So A and D are correct answers... but B is the best answer?

If you take the electricity away from an electrolytic cell, what happens? Nothing. You need electricity in an electrolytic cell. Think of it as a definition.

EDIT: Took away erroneous information.

 

[Back 5]

IDK if intellectual challenges are anything like physical ones, with a nice rest day tomorrow and well controlled anxiety on test day, it is possible that you could peak. This has happened to me many times competing as a cyclist. I would feel terrible training all week before a big race, and then come race day when it really counts, i would put my head down and just feel good the whole race. theres a study on anxiety and cognitive abilities. anxiety gradually increases cognitive ability but then drops off like a cliff at a certain blood pressure and pulse rate. the study was conducted on trauma hospital staff during pediatric emergencies. ill look it up.

Sorry, when I said "peaking" I meant "peeking" in that glancing at information that might be laying on the table or using sources other than your brain to answer the question. Not peaking as in achieving a personal record.

Fingers got a little confused at the keyboard 🙂

 

[MedGrl@2022]

Sure, which questions did you want to go over?

Passage V PS AAMC 11 Item 39

Just wanted to verify we know that Figure 2 represents a galvanic cell because it is lighting up a light bulb spontaneously since there is no battery or input of voltage. Since Cu has the highest reduction potential we take the oxidation potential of Pb and we add them together to find the Ecell? Right?

 

[Innie]

I could see where you might think D is good. Red-ox generally deals with solid and aqueous reactants/products which are only very slightly affected by pressure. However (think Verbal, here!) unaffected is not the same as very slightly affected! So D is wrong.

 

[Postictal Raiden]

this would be great...we could just drop questions at each other this evening

Yes, let's start a chat thread to discuss questions from AAMC FL's and post some clue/hints on how to read graphs and approach certain types of questions.

I just re-did AAMC 11 PS, finished it with 14 mins to spare (I did every single calculations), and got only 2 wrong (14). Yes, i know this is inflated because I took it yesterday and read the solutions for some of the questions I missed. However, my point is that I discovered that there were questions I shouldn'd have missed. Frankly, I'm still confused about why I selected the incorrect response for some of the questions while I knew the correct answer choice.

I concluded that there were some questions I would have missed regardless of how focused or how much extra time I had. Also, based on my analysis, my content knowledge would have gotten me 13, but my test taking skills what caused me to get 10.

Now, I'm moving on to do the same for the BS.

 

[MedGrl@2022]

A and D are both wrong. LeChatlier affects all reactions. Pressure is a form of LeChatlier. So its temperature, volume, concentration of reactants and products.

Edit: What I was saying earlier is that since A and D are saying the same thing, both can be eliminated immediately.

okay so pressure would affect the reaction in the electrochemical cells... I guess that makes sense...

 

[Back 5]

Question #40 on aamc#11.

The question asks us to determine the current passing through the lightbulb when 2V are passed through a similar circuit with negligible resistance compared to the lightbulb. I know the equation V=IR, but I chose C over D because the verbiage made me think the resistance would be less than .5ohms.

Was I over thinking the question?

 

[Postictal Raiden]

Question #40 on aamc#11.

The question asks us to determine the current passing through the lightbulb when 2V are passed through a similar circuit with negligible resistance compared to the lightbulb. I know the equation V=IR, but I chose C over D because the verbiage made me think the resistance would be less than .5ohms.

Was I over thinking the question?

Yes.

This is a classical example of easy MCAT questions. Don't expect every question to be tricky and hard. They need to include just as many easy questions as hard ones to produce the bell curve.

 

[Postictal Raiden]

Regarding Q. 38 of the same passage:

It was easy to eliminate options B and D simply becaues the charges on both sides don't cancel out. I chose the right answer "C" but used different rationale than the one they provided in the solution. I thought, since Cu is one of those elements that don't oxidize easily (money elements), it must be reduced and Al will be oxidized instead. Was I luck? or does my rationale also make sense?

 

[HotHamH2O]

Question #40 on aamc#11.

The question asks us to determine the current passing through the lightbulb when 2V are passed through a similar circuit with negligible resistance compared to the lightbulb. I know the equation V=IR, but I chose C over D because the verbiage made me think the resistance would be less than .5ohms.

Was I over thinking the question?

i took it to mean that it was less than .5 ohms. so it has to be 4.0A or more. 4 was the largest number in the choices so i went with it. but the question is worded terribly.

 

[Hadoken]

Howdy folks. First time poster long time lurker and a fellow 4/26'er! For that circuit question mentioned above, I I assumed that it was the circuit itself that had negligible resistance. Sometimes, the intrinsic nature of the wire can generate an innate resistance if it has low conductivity. Another way to read that would be "...if the lightbulb was the only source of resistance.

Good luck to everyone on Friday!

 

[osprey099]

Passage V PS AAMC 11 Item 39

Just wanted to verify we know that Figure 2 represents a galvanic cell because it is lighting up a light bulb spontaneously since there is no battery or input of voltage. Since Cu has the highest reduction potential we take the oxidation potential of Pb and we add them together to find the Ecell? Right?

Yup, just add it up

 

[osprey099]

Question #40 on aamc#11.

The question asks us to determine the current passing through the lightbulb when 2V are passed through a similar circuit with negligible resistance compared to the lightbulb. I know the equation V=IR, but I chose C over D because the verbiage made me think the resistance would be less than .5ohms.

Was I over thinking the question?

Yea, like Ibn said, just use V=IR and solve.